Furnace for producing carbon black



2 SHEETS-SHEET 1 //v VE/V 727R. 11 zW 5r ""Um! I G F FRIAUF FURNACE FORPRODUCING CARBON BLACK Aug. 12, 1952 Flled June 10 1947 Aug. 12, 1952 G,F, FRIAUF 2,606,819

FURNACE FOR PRODUCING CARBON BLACK Filed June 10, 1947 2 SHEETS-SHEET 2i i i E l i i i a l Q 1a 15 if g 11 VA 1 5g Fig. 3.

Patented Aug. 12, 1952 FURNACE FORPRODUCIN G CARBONELACK George F.Friauf, Pampa, Tex.,.assignor to Godfrey L. Cabot, Inc., Boston,Mass.,-a corporation of Massachusetts Applicationflune I0, 1947,,Seria'lN0. 75'3i631 '1 Claim. 1

This invention relates to the production of furnace carbon black andconsists in a new and improved burner construction which has been foundto improve both the yield and the-quality of furnace carbon black ascompared with the output of furnaces heretofore available.

In one aspect the present invention consists in improvements in thefurnace disclosed in United States Patent No. 2418,4975, granted April8, 1947, on the application of William Loving, although the invention isin no sense restricted to the furnace of that patent.

One of the most successful furnaces heretofore available to the .carbonblack industry, and

shown in the Loving patent, .includes in its structure a series ofburner pipes having a multiplicity of uniformly distributed small gasorifices from which in operation issue amultitude of gas jets. Airrequired for combustion-is supplied in a substantially straight pathpassing through the spaces provided between the burner pipes. I havediscovered that improved results may be secured in several respects byproviding each burner pipe with a row-or rows of short straight outletpipes of small diameter instead of mere orifices, and by short pipesofsmall di ameter I mean pipes or nipples having the diameter of or A"standard pipes and a length of 2" to 6".

Among other advantages'this novel construction results in a loweroperating temperature for the burner pipes themselves because theburning .jets of gas, instead of issuing directlyfrom the andunpredictable increase in the yield of carbon black produced by thefurnace. For example, all other conditions being the same, theemployment of outlet pipes of the character above described has resultedin some instancein an improvement of as much as '47 in 'theyield ofcarbon black produced in a standard .5bar Sterling burner, and moreoverthe equality :of the black produced has been improved'at leasta 'fulldegree-on the Nigrometer scale.

These and other features of the invention will be best understood-"andappreciated from the following description of a preferred embodimentthereof, selected ro'r purposes of illustration and shown intheaccompanying drawings in which:

Fig. 1 is a view-showing-a furnace partly i'n side elevation and partlyin vertical section,

Fig. 2 is a sectional view -of two burner pipes, and

Fig. 3 'is a view of one of the burner boxes in horizontal crosssection.

As indicated in Fig. 1, the burner box of my invention may be usedadvantageouslywith a horizontally disposed furnacecomprising a generallyrectangular enclosure formed by --a sheet steel casing in lined withrefractory brick H and provided at one end with an outlet duct Inpractice the furnace may be 1-2 to {24 feet in length and accordingly,in'1 it is represented as having a'section broken fromit. The -furnace isprovided at its front "end-with rectangular openings to receiveindividual burner boxes, one of which is shown in Figs. 1 and 3.Thesecomprise a sheet metal casing including sections '13 and It. Thesection 13 is bolted directly to the front wall of the furnace and isherein shown as containinga'seriesof "six vertical burner pipes l 5. 'Inpractice these pipes may be about '3 feet long and oval or pear-shapedin crosssection. They are arranged with their fiat sides spaced about /2apart and with their narrow faces directed into the furnace enclosure.

The spacing of the vertical burner pipes provides air passages betweenthem. Preferably and as shown in Fig. 2, the pipes 15 are machined attheir widest portion to provide flat surfaces It which accurately definethe Width of the air passages and insure uniformity of width from top tobottom. Each pipe I5 is provided atits top and bottom Wall with a tappedhole 17 for inlet gas connections. Each of the pipes I5 is provided inits narrow face with a row of uniformly spaced holes to receive outletpipes 18. In practice these may comprise A standard .pipe nipplesapproximatelyBWin length and they may be spaced 1" oncentersso that eachvertical-burner pipe Iiis provided with thirty-three outlet pipes I 8.The pipes 18 serve as nozzles for gas jet flames directed into thefurnace space.

As shown in Figs. 1 and 3, each vertical burner pipe 15 is connected atitsupperancl lower ends to gas headers [B by intermediate connectingpipes 20. Air is supplied to'th'e outer section M ofthe burner boxthrough a vertical duct 2! from which it is directed forwardly in asubstantially straight line path to and "between the burner pipes 15. Inorder to distribute the air and remove eddy currents from it aperforated baffle plate 22 is shown as interposed between the sections13 and M of the burner box.

The burner box above described has been operated over a range of gasrates from 4500 C. F. H. to 7500 C. F. H. with a wide variety ofdifferent air-gas ratios. The results have been unpredictably favorablein respect first to production rates which are substantially higher thanthose of the conventional burner shown, for example, in the Lovingpatent above identified. It is noted that the increase in productionrate is higher for the lower scale blacks; for example, a 77% increaseis shown for 91 scale; 54% for 92 scale; 28 for 93 scale; and 12% for 94scale on the Cabot Nigrometer, in which the lower scale numbers indicategreater intensity of black. Then in respect to operation, it is evidentthat the burner of my invention runs very much cooler than theconventional burner. This fact permits the employment of cast ironburner pipes whereas heretofore more expensive alloys have beennecessary for these elements and gasket failure has resulted fromoverheating. In operating the conventional burner, it is apparent fromobservation of the flame and observation of the burner upon removal fromthe furnace, that an appreciable amount of combustion takes placeimmediately in front of the burner pipes. On the contrary, the outletpipes employed in my improved construction are long enough to locate theburning jets somewhat beyond the probable low pressure zone in whicheddy currents would otherwise be encountered caused by air rushing pastthe vertical burnerpipes. It is probable that the improved yield derivedfrom the construction above described is due in part to the streamlinemanner in which the air and gas are brought together for combustion.

The burner box is herein shown as provided with six vertical burnerpipes 15, although the precise number is a matter of secondaryimportance and four, five or six pipes may be employed as desired.Thefollowing table gives a comparative test between a five-pipethirty-three hole burner and the same burner equipped with thirty-threestandard'pipes as shown here- From the above it will be seen that thisburner using the outlet pipe tips will produce more black of the samescale than the same burner equipped with ordinary drilled orifices inthe burner pipes. Furthermore, the greater increase in yield is in thelower scale blacks of the more intense color.

In general it has been found advantageous to operate the burner hereindisclosed with a ceiling of about 6500 C. F. H. gas rate, since abovethis the yield and properties of the product tend to show a falling off.In actual practice the burner herein described has been operatedsuccessfully under the following conditions:

4 Example 1 Gas C. F. H 5,490 Air C. F. H 27,370 Air-gas ratio 4.99Theoretical air 47.25% Cross-sectional gas outlet area 9.37 sq. in. Gasvelocity 23.42 ft./sec. Air velocity I 2.83 ft./sec. Yield 6.05 lbs. per1000 cubic feet of gas.

When compounded with rubber in a conventional test formula, the testresults were as follows:

Tensile strength lb. per sq. in 2,740

300% modulus; do 1,640

400% modulus do 2,390

Hysteresis .117

Rebound (per cent restored energy) 58.1

Example 2 Gas C. F. H 5,477

Air C. F. H 26,470

Air-gas ratio 4.83

Theoretical air 45.74%

Cross-sectional gas outlet area 9.37 sq. in.

Gas velocity 23.36 ft./sec.

Air velocity 2.74 ft./sec.

Yield 6.91 lbs. per 1000 cubic feet of When compounded with rubber in aconventional test formula, the test results were as follows:

Tensile strength lbs. per sq. in 2,470 300% modulus; do 1,700 400%modulus do 2,395 Hysteresis .108

Rebound (restored energy) 59.0

In the foregoing examples furnace temperatures of 2300 to 2550 F. wereemployed and no trouble whatever with coking was encountered. This is animportant advantage incident to the construction of my invention sincethe formation of coke upon the walls of the furnace is a seriousoperating objection that occurs frequently in furnaces which vary intheir construction substantially from that herein disclosed and claimed.For example, the use of nipples of substantially greater length than themajor dimension of the burner pipe section tends to bring about cokingin the furnace. Natural gas may be supplied to the burner at seasonaltemperature or it may be preheated. When the furnace is used forproducing H. M. F. carbon black, the yield is increased approximately25% by preheating the gas to 1000" F.

A 1500 lb. lot of so-called 105 carbon black, made with furnacetemperatures of-2490 to 2500 F. of the color intensity of 88 to 90 onthe Nigrometer scale, was readily pelletized and found to have 106% ofthe abrasion resistance of Standard Black. Standard 105 Black is socalled because, when tested in a typical tire tread compound, itexhibits 105% of the abrasion resistance of standard Easy ProcessChannel Black, the grade of channel black primarily used by tiremanufacturers.

The employment of gas outlet pipe nipples as herein disclosed has theeffect of moving the flame into the furnace sufiiciently to reduce theoperating temperature of the whole furnace front 5 to a decided andbeneficial degree. The life of the burner pipes is increased and theareas of most intense heat restricted to the inner ends of the pipenipples which are replaceable and may be constructed of refractoryalloys.

Having thus disclosed my invention and described in detail anillustrative embodiment thereof, I claim as new and desire to secure byLetters Patent:

A burner box for use in producing furnace carbon black, providing acasing, a series of burner pipes mounted in vertical parallel relationin the casing and outside the furnace, said burner pipes beingapproximately oval in cross section and arranged with their flattersides spaced from each other thus providing intermediate air passagesleading into the combustion space of the furnace, a row of gas outletpipes approximately 3" in length projecting horizontally into thefurnace in uniform close spacing from the narrower face of each burnerpipe, and a gas connection to each burnerpipe.

GEORGE F. FRIAUF.

6 REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Van Nostrand Co., New York, pages 4649.

